Our invention relates to stable transparent oil-in-water microemulsion concentrates consisting essentially of:
(i) water; PA1 (ii) one or more hydrophobic flavor or fragrance oils; and PA1 (iii) one or more surfactants PA1 (i) water; PA1 (ii) one or more hydrophobic flavor oils; and PA1 (iii) one or more surfactants
as well as a process for preparing such transparent microemulsion compositions, mouthwash compositions containing such transparent microemulsion compositions, and perfume compositions containing such transparent microemulsion compositions.
The concept of the microemulsion was introduced by Schulman and Montague, Ann. New York Academy of Science, 1961, Volume 92, page 366. Becher, American Chemical Society Symposium Series 448, ACS, Washington, D.C., 1991 contains two chapters covering microemulsions in foods: Chapter 1, El- Nokaly, et al and Chapter 2, Friberg, et al. The microemulsion system typically contains relatively large amounts of oil and water along with a surfactant and cosurfactant except in the case of certain hydrophobic surfactants where no cosurfactant may be required. These systems are indicated in the prior art to form spontaneously as a result of contact between the several components.
The most characteristic difference between an emulsion and a microemulsion is the appearance of the microemulsion an the emulsion. An emulsion is turbid while the microemulsion is transparent.
Rosano, U.S. Pat. No. 4,146,499 issued on Mar. 27, 1979 discloses a method for the preparation of oil-in-water microemulsions via a four-step process: (1) a surfactant is selected which is just barely soluble in the oil phase; (2) the surfactant thus selected is dissolved in the oil to be emulsified in an amount effective to yield a fine emulsion of the emulsified oil in an aqueous phase; (3) the oil, together with its dissolved surfactant is added to the water phase and shaken or stirred; and (4) finally there is provided a second surfactant in the water phase which is somewhat more soluble in water than the first surfactant to produce a substantially clear microemulsion of oil in water. Wolf, et al, U.S. Pat. No. 4,835,002 issued on May 30, 1989 discloses microemulsions of edible oils in a matrix of water and certain alcohols which are prepared using certain edible surfactants for use in various products such as beverages. El-Nokaly, et al, U.S. Pat. No. 5,045,337 issued on Sep. 3, 1991 discloses microemulsions which are thermodynamically stable, clear and homogeneous which are made from a polar solvent, a specific polyglycerol mono, diester and a lipid. El-Nokaly, et al discloses that these microemulsions are edible, have good flavor and can be used to disperse water soluble nutrients, vitamins, flavors and flavor precursors in oils. The polyglycerol mono diester in El-Nokaly, et al consists of a mixture of mono and diesters of branched or unsaturated fatty acids having from 12 to 24 carbon atoms and a polyglycerol mixture consisting of 0% to 10% monoglycerol and other polyglycerols, 30% of less diglycerol, 25% to 50% triglycerol, 15% to 50% tetraglycerol. Tabibi, et al, U.S. Pat. No. 5,130,122 issued on Jul. 14, 1992 discloses oral cavity and dental products prepared by microemulsifying an adsorptive oil in an aqueous medium to produce uniform submicron sized droplets. It is disclosed by Tabibi, et al that the products disclosed therein avoid the generally unaesthetic, oily, and unpleasant taste problems of previous similar products.
Nothing in the prior art discloses or implies a high flavor or fragrance loading, e.g., 25% flavor or fragrance oil in a microemulsion which has unexpectedly and advantageously high stability yet is free of lower alkanols, e.g., ethyl alcohol or contains less than about 1% of lower alkanols, e.g., ethyl alcohol.